Thermoplastic polyacetals stabilized with aminocarboxylic amides

ABSTRACT

A process for stabilizing polyacetals against thermal degradation by adding special aminocarboxylic amides of the type of Beta -aminolactamide, with or without polycondensates of isophthalic diamide, N,N&#39;&#39;-alkyleneureas and formaldehyde.

United States Patent [72] Inventors Bruno Sander;

Wilhelm Schuette, both of Ludwigshafen, Germany [2]] Appl. No. 768,158

[22] Filed Oct. 16, 1968 [45] Patented Sept. 21, 1971 [73] AssigneeBadische Anilin- & Soda-Fabrik Aktiengesellschaft Ludwigshafen(Rhine),Germany [32] Priority Oct. 17, 1967, Oct. 17, 1967 [3 3 Germany P 16 69727.1 and P 16 69 728.2

[54] THERMOPLASTIC POLYACETALS STABILIZED WITH AMINOCARBOXYLIC AMIDES 7Claims, No Drawings 52 vs. C! 260/459, @Z4 ;9.5

[51 lnt.Cl cosms/so [50] Field of Search....-

[56] References Cited UNITED STATES PATENTS 3,131,165 4/1964 Hermann etal. 260/459 3,274,149 9/1966 Berardinelli 260/45. 8 3,376,255 4/1968Wagner et al 260/4575 Primary Examiner- Donald E. Czaja AssistantExaminer- Ronald W. Griffin Attorney-Johnston, Root, O'Keeffe, Keil,Thompson &

Shurtleff a, and formaldehyde.

THERMOPLASTIC POLYACETALS STABILIZED WITI-I AMINOCARBOXYLIC AMIDES Thisinvention relates to a process for stabilizing high molecular weightpolyacetals which consist to the extent of 80 percent by weightoxymethylene units against the action of heat by the addition ofaminocarboxylic amides.

Known polyacetals of this type are the high molecular weight polymers offormaldehyde and trioxane, for example those whose terminal hydroxylgroups have been stabilized by chemical reaction such as byetherification or esterification and also in particular copolymers oftrioxane with copolymerizable compounds which introduce into the polymerchain oxyalkylene units having at least two adjacent carbon atoms, forexample with cyclic acetals or ethers which have at least two adjacentcarbon atoms in the molecule such as ethylene oxide, 1,3-dioxolane,1,3-dioxacyc1oheptane or diglycolforrnal, or with linear polyacetalssuch as polydioxolane.

It is known that polyacetals can be stabilized against thermaldegradation such as occurs for example in the processing of polyacetalsin conventional processing equipment for thermoplasts, by the additionof amides, ureas, thioureas, hydrazines hydrazides, aromatic nitrocompounds, polyamides or polycondensates of formaldehyde and diamides.

The effectiveness of heat stabilizers hitherto known is not entirelysatisfactory however for this purpose. For example, low molecular weightamides and polyamides tend to discolor the polyacetal compositions atelevated processing temperatures.

It is also known from US. Pat. No. 3,131,165 and also from US. Pat. No.3,274,149 that aminoamides exert a stabilizing effect on oxymethylenepolymers. Molding materials which contain aminoamides of the said typeas thermal stabilizers have a tendency in processing however not only tofrom troublesome coatings on molds but also to discolor.

We have now found that thermoplastic polyacetals consisting to theextent of at least 80 percent by weight of oxymethylene units can bestabilized against the action of heat by the addition of stabilizingamounts of aminocarboxylic amides with or without conventionalantioxidants without the said disadvantages by using, as theaminocarboxylic amide a derivative ofB-aminolactamide having the generalformula:

in which:

R denotes one of the groupings:

in which m denotes l to 3 and n denotes l or 2 6 denotes 1 and n denotes1 to 3 or in which m+n denote from 1 to 5 and m denotes from 1 to 5; and-R denotes either -H or -Cl-l -CH(Ol-1)-CONH We have further found thatderivatives of B-aminolactamide which contain more than one lactamideradical in the molecule are particularly suitable as thermal stabilizersfor oxymethylene polymers.

It is preferred to use nitrilotrilactamide and/orethylenediaminetetralactamide as derivatives of B-aminolactamide.

Particularly favorable results are obtained in the said process when(additionally to the said class of compound) a polycondensate is addedwhich has been obtained from isophthalic diamide, a cyclicN,N-alkyleneurea having for example two to five, particularly 2 to 3,carbon atoms and formaldehyde or a substance which yields formaldehyde.Examples of suitable cyclic alkyleneureas are N,N'-ethyleneurea,N,N'-propyleneurea, 4-methoxy-5,5-dimethyl-N,N'- propyleneurea,4-hydroxy-5 ,5-dimethyl-6-isopropyl-N ,N propyleneurea and mixtures ofthe same. Unsubstituted cyclic alkyleneureas such as N,N'-ethyleneureaand N,N'- propyleneurea are however also particularly suitable.

It is surprising that unlike molding materials stabilized with theaminoamides hitherto used the molding materials stabilized according tothis invention do not form any coatings on molds and practically do notdiscolor at conventional processing temperatures. It is also ofadvantage that these special aminoamides have a better stabilizingeffect than prior art stabilizer of the said type and consequentlysmaller amounts of additive are required for the stabilization of thepolyacetals. It is also surprising that in the stabilization ofpolyacetals with derivatives of B-aminolactamide it is necessary as arule to use smaller amounts of oxidation stabilizers than when usingprior art thermal stabilizers. The thermal stabilizers according to theinvention thus act in a synergistic manner with conventionalantioxidants such as 2,2'-methylene-bis-(4-methyl-6- tert-butylphenol)or 2,2-butylidene-bis-(4-methyl-6-tert-butylphenol).

Another advantage of the new thermal stabilizers is that owing to theease with which they can be crystallized they can be prepared in a verypure state and can easily be incorporated into the polyacetals.

The thermal stabilizers according to the invention are added byconventional methods to the macromolecular polyacetals in amounts offrom 0.05 to 5 percent, preferably from 0.1 to 1 percent, by weight withreference to the weight of polyacetal. Owing to the good stabilizingeffect, an addition of from 0.1 to 0.3 percent by weight is generallyadequate.

If a polycondensate of the above-mentioned type is also used for thestabilization, it is advantageous to use it in amounts of from 005 to2.0 percent, preferably from 0.1 to 1.0 percent, by weight and thederivative of B-aminolactamide in amounts of from 0.01 to L5 percent,preferably 0.05 to 1.0 percent, by weight with reference to the polymer.The total amount of stabilizer mixture may be up to 3 percent by weight.It is preferable however to use an amount of from 0.15 to 1.5 percent byweight.

The derivatives of B-aminolactamide used in accordance with thisinvention may be easily prepared for example by the addition ofglycidamide:

to an amine by known methods. The lactamide radical may be introducedonce or more than once. Glycidamide may be obtained for example byreaction of acrylonitrile with hydrogen peroxide in aqueous solutionaccording to US. Pat. No. 3,217,016.

The following are examples of amine components suitable for thereaction: ammonia, hydrazine, hydroxylamine, the C to C alkylenediamines such as ethylene diamine, propylene diamine-l ,2, propylenediamine-l ,3, hexamethylene diamine- 1,6, and also diethylene triamine,triethylene and tetramine and tetraethylene pentamine.

The reaction products of glycidamide with ammonia and C and C alkylenediamines are particularly suitable thermal stabilizers from thestabilizers used according to this invention. The following areexamples: nitrilotrilactamide, iminodilactamide,ethylenediaminetetralactamide, hexamethylenediamine-l,6-tetralactamideand mixtures of these, particularly mixtures such as may be formed inthe production of the said substances.

It is generally advantageous also to add to the polyacetals stabilizedagainst degradation by heat, from 0.01 to 3 percent, preferably from 0.1to 0.5 percent, by weight of conventional antioxidants for oxymethylenepolymers. Phenolic antioxidants are preferred, particularlyalkylenebisphenols, as for example2,2'-methylene-bis-(4-ethyl-6-tert-butylpheriol), 2,6-ditert-butyl2p-cresol, 2,2'-methylene-bis-(4-methyl6-tert-butylphenol)and 2,2-butylidene-bis-(4-methyl-6-tert-butylphenol. Hydrazones such asbenzaldehyde-(N-methyl)- in this stability test.

The occurrence of coatings on molds is determined in comparativeinjection molding tests in dependence on the temperature of the melt.

phenylhydrazone, piperonal-(N-methyl)-phenylhydrazone, 5 I The resultsof the tests are given in the table in which the3,5-ditert-butyl-4-hydroxybenzaldehyde-(N-methyl)-phe l. followingabbreviations are used:- M =molding material samhydrazone and mixturesof the said compounds are also very P AA f antioxidant in Percent; L055=|055 in suitable. In some cases it may prove useful to add to theWeight of the Sample after 2 hours 3! under air in P polyacetalsstabilized according to this invention, not only ancent; olo @o fter 2hours t 22 er F tioxidants but also other prior art thermal stabilizers.l0 =ter nperature at which mold coatings form in C.; 0 =color- I Thestabilizers to be used according to this invention areless;b=brown;b=yellow brown;

' TABLE Thermal stabilizer M Type Amount AA Loss Color MCF 1Nitrilotrllactamlde 0.2 0.4 0. 54 c 2 do 0.2 0.3 0.60 c

a. do 0.2 0.2 0.79 c

4. .do 0.1 0.2 0 90 c 5 thylenediamliietetralactamld 0.2 0.3 0.71 c

6. Nltrilotripropionamide 0.1 0.2 1.93 b

L man 0.2 0.4 0. 97 b 8 Dlcyanodlamide 0.2 0.4 0.96 yb -readily misciblewith the polyacetals. They may be incorw claim;

porated into powdered polyacetals, if desired together with 1. A polymercomposition comprising thermoplastic pigments, fillers a nd the like, inconventional dry mixers and polyacetals consisting to the extent of atleast 80 percent by also easily introduced in solid or dissolved forminto molten weight of oxymethylerie units and a stabilizing amount of apolyacetals. In the case of trioxane copolymers, the stabilizerscompound obtained by replacing at least one N-bound may advantageouslybe added after removal of unstable conhydrogen of ammonia, hydrazine,hydroxylamine, a C to C stituents (effected for example by hydrolytic orthermal alkylerie diamine or a polymeric ethylene diamine of formuladegradation of unstable chain segments) to the powdered or Hz H, whereinn is an integer from 2 to 4 with a lactamide granulated copolymer andincorporated by fusion and r i al of formula homogenization. Theaddition of stabilizers prior to H processing and degassing of thecopolymers has also proved to c be suitable in the case of trioxanecopolymers. 1

Polyacetals which have been stabilized according to this in- 2 A polymercomposition as la m ij ciaim 1 where", 3.3. f q i P i li qiH. a W l'iihsaid stabilizing compound is obtained by reacting glycidamidediscoloring and may be USd for the conventional uses Of OX- a compoundelected from the group consisting of am- Y Y- P y Such as the Productionof moldings, monia, hydrazine, hydroxylamine, a C to C alkylene diaminefilm arid Sheetingand a polymeric ethylene diamine of formula Thefollowing examples illustrate the invention. The parts 40 andpercentages given in the examples and comparative ex- 2 -L- r i- J Hperiments are by weight. wherein n is an integer from 2 to 4. EXAMPLESAND COMPARATIVE EXPERIMENTS (cf A fil as f i i l Table) sa d stabilizingcompound is obtained by addition of glycidamide to ammonia.

A sample of a copolymer from 97 percent of trioxane and 3 4. A polymercomposition as claimed in claim 2, wherein percent of 1,3-dioxolane(which has been fused and degassed said stabilizing compound is obtainedby addition of glycidain a degassing screw with an addition of 0.02percent of sodimide to ethylenediamine. um fluoride and the variousamounts of 2,2-methylene-bis-(4- 5. A polymer composition comprisingthermoplastic methyl-o-tert-butylphenol) indicated in the table asantioxipolyacetals consisting to the extent of at least 80 percent bydam) is processed on an extruder with various amounts of the weight ofoxymethylene units and a stabilizing amount of thermal stabilizers setout in the table to form a granulate. nitrilotrilactamide orethylenediaminetetralactamide.

The stability of the various stabilized molding material is 6. A polymercomposition as claimed in claim 5, wherein determined by measuring theloss in weight of samples after said stabilizing compound isnitrilotrilactamide. they have been heated for 2 hours at 222 C. whilepassing air 7. A polymer composition as claimed in claim 5, wherein overthem. The degree of discoloration may also be detected said stabilizingcompound is ethylenediaminetetralactamide.

mg?" UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.5,607,831 Dated September 21. lQYl Inventor) Bruno Sander and WilhelmSchuette It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 23, "hydrazines hydrazides" should read hydrazines,hydrazides Column 2, line 61, "triethylene and tetramine" should readtriethylene tetramine Column 3, line 2, "ditert-butyl2p-oresol" shouldread ditert-butyl-p-cresol line A, "tylphenol" should read tylphenol)Column 4, line 11, "biyellow" should read yb yellow line 50, claim 1,"HZN H" should read Signed and sealed this 18th day of April 1972.

(sEAL) Attest:

EDWARD MJ LETCHERJR. ROBERT GUT'I'SCHALK At testing Officer Commissionerof Patents

2. A polymer composition as claimed in claim 1, wherein said stabilizing compound is obtained by reacting glycidamide with a compound selected from the group consisting of ammonia, hydrazine, hydroxylamine, a C2 to C6 alkylene diamine and a polymeric ethylene diamine of formula H2N CH2-CH2-NH nH, wherein n is an integer from 2 to
 4. 3. A polymer composition as claimed in claim 2, wherein said stabilizing compound is obtained by addition of glycidamide to ammonia.
 4. A polymer composition as claimed in claim 2, wherein said stabilizing compound is obtained by addition of glycidamide to ethylenediamine.
 5. A polymer composition comprising thermoplastic polyacetals consisting to the extent of at least 80 percent by weight of oxymethylene units and a stabilizing amount of nitrilotrilactamide or ethylenediaminetetralactamide.
 6. A polymer composition as claimed in claim 5, wherein said stabilizing compound is nitrilotrilactamide.
 7. A polymer composition as claimed in claim 5, wherein said stabilizing compound is ethylenediaminetetralactamide. 